The prior art embraces machines of the type in question, which comprise a dispensing disc rotatable intermittently about a vertical axis and furnished with a ring of cavities, each containing a quantity or portion of tobacco that will correspond to the contents of a single pouch.
The portions are released into the single cavities at a filling station by a hopper containing a supply of powdered tobacco, en masse, treated with flavouring and moisturizing agents.
Downstream of the filling station, the machine comprises skimming means that serve to remove any excess tobacco from each of the cavities.
With the disc in rotation, the cavities are carried beyond the skimming means and toward a transfer station where the single portion of tobacco contained in each cavity is ejected.
Installed at this same station are pneumatic ejection means comprising a nozzle positioned above the dispensing disc. At each pause in the movement of the disc, a portion of tobacco is forced by the nozzle from the relative cavity into a duct, of which the mouth lies beneath the disc and in alignment with the nozzle, and directed toward a station where the single pouches are formed.
The forming station comprises a tubular element, placed at the outlet of the duct and functioning as a mandrel over which to fashion a tubular envelope of paper wrapping material.
The material in question consists in a continuous web decoiled from a roll and fed in a direction parallel to the axis of the tubular element, which is wrapped progressively around the element and sealed longitudinally.
Beyond the tubular element, the machine is equipped with transverse sealing means of which the operation is synchronized with the transfer of the tobacco portions, in such a way that each successive portion will be sealed in a relative segment of the continuous tubular envelope of wrapping material delimited by two successive transverse seals.
The successive tubular segments of wrapping material, formed as pouches containing respective portions of tobacco, are separated into discrete units through the action of cutting means positioned downstream of the transverse sealing means.
A conventional machine of the type outlined above, while dependable, is nonetheless limited in terms of operating speed and unable to match the tempo of other units, connected directly downstream, by which given numbers of the single pouches are assembled in packs for distribution.
Above certain operating speeds, in effect, and especially when handling tobacco with a high moisture content, there is no guarantee with machines of the type described above that the quantities of tobacco supplied to the form-fill-and-seal station will be portioned accurately and repeatably over time.
This is due to the fact that a correct transfer of the single portions of tobacco is conditional on each cavity remaining in the transfer station for a given minimum period of time, sufficient for the pneumatic means to remove the contents of the selfsame cavity completely.
The object of the present invention is to provide a machine for manufacturing single pouches of smokeless tobacco that will be unaffected by the drawbacks mentioned above in connection with machines of the prior art, and able to combine a high production tempo with an accurate and constantly repeatable transfer of tobacco portions into successive pouches.